From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF492C433E1 for ; Mon, 24 Aug 2020 09:41:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B246D2071E for ; Mon, 24 Aug 2020 09:41:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598262065; bh=q2KANpMGXSeyzKEWZM9I8ni3OZPfwzMBznz7DQYRhiE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=c3bT4eESp8YuIgnblaqemgkfBtE5X5GByx3rUuq2Z/6vmJ136kqgwW9lgpdJdAr4G kWDHk/bepUZsFDuCAWQ2Vj0EQhegAKllMBKCGB4K7o+lnQ+4Ppnz5Sx8xBk7wtQbFe 77frwWQ0fDFL7r6B5pOI/eQLmKwfjku+JrdNdsOg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729317AbgHXJlC (ORCPT ); Mon, 24 Aug 2020 05:41:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:42810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729241AbgHXIpg (ORCPT ); Mon, 24 Aug 2020 04:45:36 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0140B204FD; Mon, 24 Aug 2020 08:45:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598258735; bh=q2KANpMGXSeyzKEWZM9I8ni3OZPfwzMBznz7DQYRhiE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pRN7qhDl+yC+4UyfyJtRDzb7WHFxsHrcdxMETx92RxCE8lGXAkO7pL1cX8alBFXsn kCt4mVyI1y7W0+vkbOkrBBwDMLz6n3mQjAjAIcCkVQqewdWdnodbR7u7fCl8VkrL5e FcHlgliogRHOSmY9+tSnN90ySV9KvACp6MdHuOC8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Andrew Morton , David Howells , Linus Torvalds Subject: [PATCH 5.4 026/107] romfs: fix uninitialized memory leak in romfs_dev_read() Date: Mon, 24 Aug 2020 10:29:52 +0200 Message-Id: <20200824082406.395752684@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082405.020301642@linuxfoundation.org> References: <20200824082405.020301642@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jann Horn commit bcf85fcedfdd17911982a3e3564fcfec7b01eebd upstream. romfs has a superblock field that limits the size of the filesystem; data beyond that limit is never accessed. romfs_dev_read() fetches a caller-supplied number of bytes from the backing device. It returns 0 on success or an error code on failure; therefore, its API can't represent short reads, it's all-or-nothing. However, when romfs_dev_read() detects that the requested operation would cross the filesystem size limit, it currently silently truncates the requested number of bytes. This e.g. means that when the content of a file with size 0x1000 starts one byte before the filesystem size limit, ->readpage() will only fill a single byte of the supplied page while leaving the rest uninitialized, leaking that uninitialized memory to userspace. Fix it by returning an error code instead of truncating the read when the requested read operation would go beyond the end of the filesystem. Fixes: da4458bda237 ("NOMMU: Make it possible for RomFS to use MTD devices directly") Signed-off-by: Jann Horn Signed-off-by: Andrew Morton Reviewed-by: Greg Kroah-Hartman Cc: David Howells Cc: Link: http://lkml.kernel.org/r/20200818013202.2246365-1-jannh@google.com Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/romfs/storage.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/fs/romfs/storage.c +++ b/fs/romfs/storage.c @@ -217,10 +217,8 @@ int romfs_dev_read(struct super_block *s size_t limit; limit = romfs_maxsize(sb); - if (pos >= limit) + if (pos >= limit || buflen > limit - pos) return -EIO; - if (buflen > limit - pos) - buflen = limit - pos; #ifdef CONFIG_ROMFS_ON_MTD if (sb->s_mtd)